How to Build a PC Controlled RC Car
August 2004
Introduction
The Mini RC Car Project has been one of my favorites to do. If you haven't checked that project out, please read through that one before starting on your own. I've gotten a few e-mails requesting a guide and since the software is done, all that is required is to construct the hardware. This is the second time I've done this project, using totally two completely different cars. The remote PCBs (electronics) were almost identical in both, so I'm assuming most all mini rc remotes are very similar, so this guide should be able to apply to all makes and models.
Tools and Materials Required
| - Mini RC Car & Remote - (5) Wires 1-2ft long (or 1 cat5 network cable) - Misc. small wires - Drill - Wire Stripper (or knife) - Screwdriver(s) -Scissors or Wire Cutters -Small piece of plastic or plexi-glass - *Some basic soldering skills |
- Soldering Iron - Solder - (4) 2N3904 NPN Transistors - (1) Small solder board - Male Parallel Port Connector - Digitial Multimeter if Avaliable Total Cost: (not including tools) Approx - $20.00 cdn |
 (Most of the tools required, all laid out) |
 (Retract-a-bit Mini Screw Driver. Very Useful) |
 Transistors and Solder Board |
|
 Drill |
Step One: Open Remote and Expose PCB
With the antena unscrewed, remove the 3 screws from the back of the remote. You will need a fairly small screwdriver.
 1 - Screw Hole Locations |
 2 - Buttons and Screw |
 3 - Attached still |
 4 - The PCB is free |
The following corresponds to the pictures
above:
1 - Screw Hole Locations
Remove the screws and the remote face
should come off easily.
2- Take note of the button locations
and remove the bottom right screw holding
the PCB in place.
3- The PCB is still attached. Snip
the wires close to the circuit board,
but leave enough of the wire to identify
the colour, for when re-attaching later.
4- The PCB should now be free,
making it easier to work on.
Step Two: Drilling the Remote Case
 |
In order to get a cable that goes from the back of the remote's PCB to the computer, we need to make a hole in the remote's plastic case for the wires to go through. Any size hole will do, as long as it's big enough for your wires to fit through. Drill the hole closer to the back of the remote, if possible. That just makes it so the cable won't have to bend as much. |
Step Three: Soldering to the Board
| Strip the ends of the wires. Five wires, about 1-2 ft in length are needed. I used a Cat-5 network cable that has 8 wires in it, but only 5 are required. |  |
| Turn over the PCB (printed circuit board). Under each button there are four solder joints. These are actually (2) sets of (2) joints. These are highlighted in the picture on the right. Identify the wire that the negative side of the battery was connected to (see wire indicated in the picture). This will connect to one of the large green areas on the board. For each switch, two of the solder joints will be located in this green region. Leave those joints alone. |  (Click for a Larger Image) |
 (Click for a Larger Image) |
What we are concerned with, is the positive "side" of the switch. For each switch, you need to identify which side is negative and which is positive. Solder a wire onto each positive side and one wire to a negative terminal (there are many negative terminals on the PCB, it doesn't matter which you choose). You should have 1 wire per switch soldered, and one wire to the negative terminal. My board, with the wires soldered can be seen to the left. Boxes are drawn in to show the same groups of four shown above. |
Step Four: Build the PC Interface
This is the most callenging part of
the project.
Before you start building the cable, feed
the wires you soldered, through the hole
you drilled earlier. This will allow you
to put it all back together again at the
end.
 |
Take the male parallel port connector and solder short wires to pins 2,3,4,5,23. Pins 2-4 will carry the data (forward, reverse, left, right) and pin 23 is ground. Side note: when doing any pc-parallel port interfacing, pins 2-9 are easily controlled data pins and pins 18-25 are all ground. Other pins have specialty functions and can be used in interesting ways. When completed, it should look similar to the picture on the left. |
|
 |
Parallel Port Pinout (Click for Larger Image) |
|
The rest consists on building a circuit, using the schematic (diagram) I have made up. For this you need, a bunch of small wires, solder board, (4) 2N3904 NPN Transistors. Print out the schematic below and build the circuit. (Note: the ground is the Parallel Port Pin 23 and Remote Negative Terminal connected together, there is no 'third' ground.)
 (Click for a Larger Image) |
Pictures of Circuit Construction:
Follow the schematic, but these may help you
out. These pics do not show full construction.
|
 |
 |
 |
If you've followed the schematic and completed the following steps properly, all we have left to do is re-attach the wires cut at the beginning and put everything back together.
Step Five: Reattaching the Wires
In the first step, you cut some wires. Those will now need to be re-attached. I would suggest replacing them with your own wires and use longer ones. The factory wires are very cheap and it's a lot easier just to use wires double as long, so you have enough room to solder them to where the old wires use to be. You can always just strip the old wires are re-attach using electrical tape, but I think my way is easier. The choice is up to you.
Step Six: Reassembly
 |
The remote needs to be re-assemled. Squish down all the wires down on the back of the PCB and put the screw back in. It might take several tries to get it flat enough, because there's a lot more wires back there than there use to be. Put back on the plastic remote face and replace the screws in the back of the remote. The remote should look very much like how it started, but with a large bunch of wires sticking out the side. |
 |
After the remote is put back together, the hardware aspect of the project is complete! |
Making it Look Nice
 |
To make it easier to plug in, it's best to have a solid unit to plug into the back of the computer. I took a small piece of plexi-glass and glued all the components to it to make it sturdier, easier to handle and it makes it look a whole lot better. |
 |
Software
The remote will still function normally if you use it just by pressing the buttons, but to control it with the computer, software is needed. For my grade 11 final computer science project, I built this hardware and wrote the software to control it. To control what you've just constructed, you will need the software as well. It is avaliable in the downloads section. To make the software work, you need to know the port address of your parallel port. In the documention included (documention.doc, in the zip file), there are clear instructions how to find this address. The most common address (888) is the default. The software was written in Visual Basic 6, and was recently updated to run on all windows operating systems.
Quick Lesson: How it Works
With the software, the computer sends a signal from the parallel port to the transistor. The transistor closes the circuit between the ground and the positive side of the button switch. This is the exact same thing that happens when you press the button manually. So essentially, the computer is pressing the buttons for you. Because we can control the computer, it means we can make the car programmable and other neat stuff like that.
Conclusion
I hope you've enjoyed this guide and learned something along the way. If you do construct your own Computer Controlled RC Car, and send me a pic I will post in on the site. If you have any feedback or questions let me know and I'll be glad to help. If you have any difficulties along the way, let me know and I'll try to help you out. Controlling the parallel port is quite easy and it opens to door to a whole lot of PC-Hardware interfacing. With transistors, you can control motors or other electronics. My latest pc interfacing project was my grade 12 computer science project, which was to control an LED matrix of 140 LEDs, with just the handful out outputs of the parallel port (some additional electronics were required). That project will soon be posted in the projects section.
Comments
hi, can you control a car with a pc wheel? (like logitech g25)
Posted by amfito on 2010-08-24 @ 13:21
hey how would i be able to do this with two motors instead of a steering mechanism. im working on trying to do this to a rc tank and wondering what i have to do different to the pcb.
Posted by Stephen Solovyov on 2010-08-22 @ 08:19
hmMm..do i needed to have inpout32.dll on my system32?? or not...
Posted by bLa2 on 2010-08-11 @ 00:47
hmMm..frm port, it outputs 5v right??? wat if my remote control is lesser or higher than the output of the port?? what could happen?? which one is needed.. or what should I do?? to protect my computer.. is my computer be damaged if my RC batry(V) is higher or lower or is my RC would work if my RC batry(V) is higher or lower than the output voltage frm port..
Posted by jstDoinPureElectrnix on 2010-08-11 @ 00:43
weLL... you can put any signal lights on it..
hmmMmm... jst an idea... you can connect it to your transmitter so that your led will work..
hmmMm...jst trying..haha!!...to have a cute one..
haha!
Posted by jstDoinPureElectrnix on 2010-08-11 @ 00:10
hmm... I thnk... to protect your PC...u need a buffer... HEX buffer i thnk ...
from parallel port to your hex buffer...then to your transistors base..
I dnt know..
not sure bout it...
Posted by JstMakinPureElctrnix on 2010-08-11 @ 00:02
My Remoe Control operates at 3V (2 Bateries). Therefore, I would like to know the mechanism to reduce the parallel port output to 3 volts. Pl tell me if I can still connect it as per the above circuit diargam without reducing the output voltage.
Posted by Rock on 2010-08-6 @ 00:25
The parallel port doesn't have enough power to drive relays. So you could use the parallel port do drive the transistors to drive the relays, but that would defeat the point.
Posted by Jon on 2010-08-1 @ 10:22
i can replace the transistor with the relay?
Posted by riko4628 on 2010-08-1 @ 09:02
Thanu u very much...
info u provided regarding parallel port interfacin is relly helpful....
Posted by rohit on 2010-07-19 @ 23:17
i want to ask how can we connect this car through usb
plese tell me
i want to connect it throutg usb
Posted by Deepak on 2010-07-19 @ 21:50
Is this circuit safety for the computer(C.P.u.)
Posted by Hash on 2010-06-30 @ 09:24
will this software work on windows 7?
Posted by jaskaran on 2010-06-16 @ 03:08
great work.thks
Posted by biduri h on 2010-06-15 @ 05:12
Alright! I need to know how about the RC´device voltage? Is it 9 or 5 volts? If 9v, maybe will damage the PC because the LPT interfce it´s limited to works on max. 5v in/out...isn´t? Let me know How Do you Do that? I will be really thankful?
Mail me, please!
Posted by Ricao on 2010-05-27 @ 15:25
can we connect the wires directly to the male parallel port from the remote
Posted by john on 2010-05-2 @ 04:20
I just want TO TELL YOU COULD DO IT. AND NOW I WANT TO DO THAT WHICH CONTAINS THE ROUTER. BUT NOT VERY WELL UNDERSTAND HOW IS.
CAN YOU SEND ME SOME MORE INFORMATIN EXPLAINED FOR THE ONE W/ THE ROUTER.
PLEASE!
THANK YOU
Posted by Alfredo on 2010-04-21 @ 09:23
can i used your software using usb to rs232 serial chord instead of db25?
Posted by jardine on 2010-03-30 @ 01:40
its realllllly goooooood!!!!!!!!!!
Posted by Riton on 2010-03-13 @ 00:37
i have built a robotic arm ..now i want to control it via remote control using USB BLUETOOTH/wifi.can you help me...
Posted by nabeel on 2010-03-7 @ 01:37
please send me hardware connectivity code as well as application....
Thanks
Posted by mital on 2010-02-23 @ 05:26
Hi,I would like build the same thiing but my laptop hasnt got a parallel port.How do i workaround?
Can i use the com port/usb port?
Posted by Jithin on 2010-02-21 @ 10:16
Great project, I used a usb interface board to control mine, I'm working on getting proximity sensors to work with the car. You can check mine out at http://ozirock.webs.com/ if you wish.
Posted by Ozirock on 2010-01-21 @ 16:33
Hi Jon,
Awesome web site. You are very bright guy and a great resource! Thank you for all the write ups here. Keep up the great work and keep us posted :-)
-Ben-
Posted by Ben on 2010-01-4 @ 05:28
nice information i m trying to contol rc helicopter through pc can u give me information about it with circuit diagram
Posted by praneet on 2009-12-6 @ 03:59
i like electronic. i need idea with that
Posted by bishry on 2009-12-3 @ 11:14
for the guy who is asking about if his remote is mere than 5 volts take it from an external powersuply or from inside the pc [yellow and black cables]
Posted by bob on 2009-11-8 @ 04:35
are the ground on the pcb and the parrarell port conector conected together
Posted by garry on 2009-11-7 @ 06:08
SUBHAM:
you have to buy a wireless cam first and reciever, than you have to buy a tv card that has audio and video inputs, than you have to connect it to your computer. after that you can see the cam on youtr screen and with this project you can control your car. and with the software of your tv card you can record it, Hope this helps...
Posted by Circass on 2009-10-8 @ 11:13
please give me idea how can i record from camera tahat connect in car
Posted by subham on 2009-10-8 @ 01:21
Hi, i m trying to make same thing but my remote is a little bit different than yours and i cant find the exact points on it. Can you tell me how to define the joint points ? Respect of what we will determine them ?
Thanx.
Posted by Circass on 2009-10-7 @ 10:37
Hey! I was wondering if you could disconnect this of a computer and just plug it into a different one (maybe mac)?
Posted by Natalie on 2009-10-5 @ 16:47
you can use some 1kohm resistors between the computer and the transistors . that will safe themselfe
Posted by abcdanonymus on 2009-09-30 @ 09:33
...ei what are the other elecronic materials needed?????
Posted by jell on 2009-07-28 @ 19:46
hey I was soldering and ended up soldering 10, and 11 together. Can I use another pin?
Posted by mac on 2009-07-19 @ 17:24
here you don't use battary, so you get charge from pc 5v ,so what if my remote use more than 5v
Posted by sherif on 2009-06-27 @ 12:20
I like cheese
Posted by fsdfsdfd on 2009-06-5 @ 10:21
fish
Posted by haha on 2009-06-5 @ 10:21
hy,
I am a novice in this area, but i want to build a car that is controlled from the computer.can someone tell me with what to start?first i want to buy a mini car but i don't know what kind of car to buy,what to look at when buying it.thanks!
Posted by Suciu on 2009-06-2 @ 12:04
It looks to complicated for me
Posted by mikuru on 2009-05-20 @ 01:54
i want to make pc controlled wireless vehicle using zigbee with feedback sensors like temperature,humidity,smoke,light intensity..
i need the relevent data or any usefull material.
moreover i would like to know is there any modification is possible
Posted by rathin on 2009-05-12 @ 22:48
i want to make this project can any body help me to make this.
i want to control only through pc not to through remote.
plz help me to make this types of project
Posted by zafar on 2009-05-8 @ 02:06
IF I WANT TO USE PARALLEL PORT AS INPUT ie. TAKING +5V WHEN SWITCH IS PRESSED & 0V WHEN NOT PRESSED. HOW SHOULD I GO ABOUT?
Posted by SAMARESH on 2009-05-5 @ 01:44
how can a rc cntrol the car with a thrustmaster ferrari steering wheel
Posted by stephan malan on 2009-04-14 @ 03:21
can this be done on a serial port instead of a parallel port? I'm trying to do something similar to this, but using a Wii-mote to control the car through a DE2 board and the board only has a serial port on it to attach to the RC remote.
Posted by eric on 2009-03-31 @ 13:57
DMCA Notice ON www.smouch.net/lol
Posted by DMCA on 2009-03-16 @ 20:55
my id is niket_united@yahoo.com ,, pls send me ur suggessions on this id..
Posted by niket on 2009-02-21 @ 08:59
hey man, i made the car,. but all i need is that i have to write the programme in turbo c++...can u help me in making the code ., i really need help.. anybody reply to this comment plss.
Posted by niket on 2009-02-21 @ 08:58
greta work.........
but its not working for me.........
the car begins to run at the moment i connect the parallel to the system..........
please help me to solve this............
Posted by vinoth on 2009-01-21 @ 05:21
>>do i have to put a resistor at the base of the transistor?
ANS: It would be a good idea to, but in practice isn't needed. Your call.
>>can i also insert a zener diode at the collector side of the transistor to protect the parallel port?
ANS: That shouldn't be necessary.
>>and lastly do i have to insert the battery of >>the remote control transmitter for the hardware >>to operate?
ANS: Yes you do.
Posted by Jon on 2008-11-9 @ 14:35
nice document it will help me in my project..
do i have to put a resistor at the base of the transistor? or at the emmiter? can i also insert a zener diode at the collector side of the transistor to protect the parallel port? and lastly do i have to insert the battery of the remote control transmitter for the hardware to operate?
thank you for the answers and more power :D
Posted by Photon on 2008-11-4 @ 06:44
very well designed......
Posted by RAVI on 2008-10-21 @ 07:13
do i need to put battery back in the rc during connecting to pc??? or just pc will give the current to that rc
Posted by zul on 2008-10-15 @ 13:03
hi ....
instead of 2N3904 NPN Transistors can we use this one BC547 transistor ...???
plz reply me...
thank you
Posted by sarthak on 2008-09-3 @ 08:22
I want to add some other things in this project to make it innovative .Plz give me some idea .
Thank you.
Posted by summ on 2008-08-19 @ 02:18
Do I need restistor to build cuircut using this tranistor? If yes, how much it is value?
Posted by fat comp on 2008-08-19 @ 01:25
great keep it up !!!!!!!
i am also planning to install a wireless web cam on it
Posted by gaurav on 2008-04-5 @ 05:42